At noon Mountain Standard Time on October 24, 2011, a coronal mass ejection from the Sun hit the Earth, strongly compressing its magnetic field and sparking an intense geomagnetic storm, reaching a peak planetary K index of 7. By the time dark had fallen enough here to see the aurora, the K index had fallen to 6, though still classified as "storm level". The result was a spectacular display, including red, as well as exceedingly rare blue and purple aurorae.